Without limiting the scope of the invention, its background is described in connection with methods for manufacturing 3D objects, structures, and 3D structural electronic, electromagnetic, and electromechanical components and devices.
The application of additive manufacturing to 3D electronics is still in its infancy. Large-scale adoption has been limited due to the low reliability, low performance, and high cost of current low temperature cured, conductive ink-based technology. As a result, traditional printed circuit board (PCB) technology continues to dominate the electronics industry. Advancement of 3D electronics is primarily limited to a small number of researchers across the world, most of whom are pursuing conductive ink technologies. An exception to this is the Molded Interconnect Device (MID) which involves an injection molded part that is exposed to a selective laser etching process, known as laser direct structuring (LDS) and subsequent electroless plating. These devices exhibit some 3D freedom and have seen widespread use in the automotive and personal communications markets; however, they are limited in application in comparison to the current invention since the conductive traces that result from the plating process are restricted to the exterior surfaces of the molded part that are accessible to the etching laser, and therefore cannot exhibit the embedded, multi-layer capability of the current invention. Moreover, these electroless plating processes provide limited cross-sectional area of the fabricated conductor and consequently limit high current capability.
Efforts thus far to create 3D structural electronics using additive manufacturing (AM) processes (with the processes as described and defined in ASTM 2792-12a) have centered on the use of conductive inks dispensed in direct-print (DP) (also known as direct-write (DW)) or other processes to provide electrical interconnects between components. U.S. Pat. Nos. 7,658,603 and 8,252,223 dated February 2010 and August 2012, respectively, describe in detail the integration of fluid dispensing technology with stereolithography and other AM processes to create 3D circuitry. These low temperature cured inks have weaknesses in both conductivity and in durability, which limit the application of AM fabricated 3D structural electronics to simple devices that are not subject to mechanical shock, vibration, large current or power densities, temperature extremes, or applications with high reliability requirements.
U.S. Pat. No. 6,626,364 issued September 2003 describes a method of rapidly embedding antenna wire into thin thermoplastic smart cards using an ultrasonic horn mounted on a motion control system and employing a mechanism to supply antenna wire through the horn to the work surface. The antenna wire is ultrasonically embedded in a flat, smooth, and solid plastic sheet.
There is, however, a need for methods and systems for embedding a filament (e.g., wire, mesh, etc.) in a thermoplastic device during the fabrication of a geometrically complex and intricate 3D structure with embedded electronics, sensors, and actuators. There is also a need for improving the mechanical performance of AM-manufactured 3D parts as has been stated by Ahn et al., where the ultimate tensile strength of test parts made from acrylonitrile butadiene styrene (ABS) and produced using fused deposition modeling (FDM), a well-known material extrusion AM process, was about 10-73% of a mold injected part of the same material (UTS of 26 MPa). This gap in mechanical properties between AM-produced parts and injection molded parts extends past tensile properties to include impact, flexural, compression, creep, and fatigue properties, which collectively limit the application of AM-produced parts to prototypes.